This invention relates to a coalescence separator, and, more particularly, to a coalescence separator comprising a tank for a supplied liquid having an inlet and an outlet, a coalescence element through which the supplied liquid flows, a drain for oil collected in the tank arranged in an upper area of the tank, and a drain arranged in a lower tank area for water accumulating in the tank, the drain for the water being provided with an ascending pipe.
During air compression by way of oil-lubricated screw compressors, a portion of the lubricating oil will necessarily also reach the compressed air. It is therefore necessary to provide an oil separator which is capable of filtering a large portion of the oil content out of the air. However, during the cooling of the compressed air, an amount of condensate liquid will again be obtained which consists to a large part of water caused by the humidity content of the air, and this water carries along a portion of the oil. The oil contained in the condensate is very finely dispersed or partially emulsified in the water.
It was found that a settling or calming-down of this condensate in corresponding tanks does not have the result that all oil precipitates on the surface and can be separated there. A treatment of this air compressor condensate is therefore absolutely necessary because it usually has a residual-oil content of from 30 mg to 200 mg per liter.
A coalescence separator of the above-mentioned type is described in EP 319 713 (A2). This known separator has a tank for liquid with an inlet and an outlet. The inlet and the outlet and the liquid level in the tank are situated at approximately the same height. A filter with a coalescing effect is arranged below the inlet and the outlet. During the operation of the coalescence separator, a light liquid layer is formed above the filter which must be drained from time to time.
A disadvantage of this coalescence separator is the fact that a continuous operation is not possible because of the required cleaning intervals. In addition, because of the arrangement of the inlet and the outlet in the upper area of the separator, a very strong swirling of the fed liquid is caused which has the result that the separated light liquid or the oil may possibly mix again with the water and therefore an optimal separation of the water and the oil will no longer be possible.
Furthermore, from the published brochure "Ovamat--The Clean and Safe Oil-Water Separator for Condensate" of the Beko Kondensattechnik, a system is known for the separating of the oil in which the dispersed or slightly emulsified oil constituents are to be adsorbed by an activated carbon filter. A disadvantage of this system is the fact that the service life of the activated carbon depends, on one hand, considerably on the degree of dispersion or emulsification of the oil in the water, and the filter must therefore be exchanged frequently. Also, because of the arrangement of the water drain in the area of the oil drain, there is the risk that in the case of a faulty handling, oil may reach the water drain and therefore significantly impair the effect of the system. Moreover, activated carbon cannot adsorb emulsion droplets. These droplets deposit, if they deposit at all, on the exterior structure of the activated-carbon particles.
DE-OS 28 00 344 describes a process and an arrangement for separating emulsions by way of coalescence. In a tank, a coalescing bed is provided which is further developed in a lengthening by a hydrophobic material lining. While the draining of the cleaned water takes place in the lower area of the tank and is guided via an ascending pipe, the drain for the separated oil is arranged in the upper area of the tank. A disadvantage of this arrangement is the fact that the exchange of the coalescing bed requires very high expenditures and a complete emptying of the tank is required. In addition, fed air contributes to a swirling of the layers which may lead to a subsequent mixing of the separated media.
It is therefore an object of the present invention to provide a coalescence separator which is maintenance-free and permits a simple exchange of the coalescence element, in which case a swirl-free method of operation results in a high efficiency and therefore in a very high degree of separation.
This object is achieved in accordance with the present invention by arranging the coalescence element on the tank and configuring the element as a change element, and also by providing a guide body in the tank to which an ascending cylinder is connected, with the ascending cylinder extending to an area of the liquid level.
It is a significant advantage of the invention that it is ensured in any operating mode that no oil can reach the water outlet. This advantage is achieved by the fact that, on one hand, the water drain is arranged in the lower area of the tank for the liquid and is equipped with an ascending pipe, and on the other hand, achieved by the arrangement of the oil drain which is situated above the upper edge of the ascending pipe. Since oil is lighter than water, it is ensured that no water can reach the oil drain.
Even when it is assumed that no oil is situated in the liquid tank, because of the communicating pipes, this water level will rise only to the maximum height, corresponding to the height of the ascending pipe, with a rising water level.
It is another advantage of the present invention that the separator operates in a maintenance-free manner. No exchange of any filter elements (such as, for example, activated carbon filters) is necessary. The coalescence element, which consists of a fine fiber (e.g., of a microfiber glass winding) does not require cleaning, unless other constituents to be filtered out reach the coalescence separator, in addition to the water or the emulsion.
If air is carried along with the emulsion, as might occur when compressors are used, there will be no impairment of the function of the coalescence separator because the ascending liquid flow and the air bubbles will be guided upward in a targeted manner in the area of the liquid that is close to the center.
The arrangement of the inlet for the emulsion in the lower area of the tank and the arrangement of the oil outlet in the upper area of the tank is another advantageous feature which also prevents a swirling together of the liquids.
Yet another advantage of the present invention is the avoidance of any electrical sensors which are normally provided for the outlet of the floating oil or the outlet of the remaining liquid mixture. Specifically, the use of such sensors is critical on a coalescence separator because they become dirty very easily and are therefore impaired in their operability.
According to a further embodiment of the present invention, the coalescence element is provided with a guide body on its upper end on which the oil droplets will rise which are formed on the coalescence element. This guide body assures that the oil droplets cannot swirl in the lower area of the tank for the liquid and can be discharged together with the collected water via the ascending pipe. By way of the guide body, the oil droplets are guided into the separating zone and can rise to the liquid surface.
Another advantageous aspect of the present invention is the provision of a boundary layer measuring probe for the determination of the maximal oil content in the liquid filter. By virtue of this probe, a monitoring of the oil quantity that is maximally permissible in the tank can be carried out, in which case an analysis unit is arranged behind the measuring probe and generates a signal as soon as the maximal oil quantity is exceeded.
Another advantageous feature of the present invention is distinguished by the fact that an ascending cylinder is arranged in the tank for the liquid. This ascending cylinder follows the guide body and consists, for example, of a wire netting. The ascending cylinder removes air bubbles, which are still carried along in the condensate, in the upward direction without any swirling.